JP3471255B2 - Nonwoven fabric for battery separator and battery using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is, nickel - cadmium battery, a nickel - zinc batteries, nickel - non-woven fabric suitable cell separator such as an alkaline storage battery such as a hydrogen batteries
And a battery using the same .

[0002]

2. Description of the Related Art Conventionally, a nonwoven fabric made of a polyolefin fiber is hydrophobic and, for example, has poor wettability when used as a battery separator. Therefore, there are various methods for hydrophilicizing a nonwoven fabric made of a polyolefin fiber. Proposed. Examples of the hydrophilic treatment method include sulfonation treatment, fluorination treatment, corona discharge treatment, and vinyl monomer graft polymerization treatment. In particular, the sulfonation treatment is useful for improving the self-discharge property of the secondary battery, and various methods have been proposed. For example, Japanese Patent Laid-Open No. 1-
In Japanese Patent No. 132042 and JP-A No. 1-132044, after polypropylene fibers are opened and dispersed, they are evenly sprinkled in an organic solvent in which polyethylene is dispersed to impart a binding property to the polypropylene fibers, and There is disclosed a battery separator in which fibers are heat-sealed to each other by passing between heat rolls to form a nonwoven fabric having polypropylene inside and polyethylene near the surface layer, and a polyethylene portion is sulfonated by a sulfonation treatment. Further, in JP-A-7-278963, there is disclosed a battery separator in which a syndiotactic styrene polymerization component having a glass transition temperature lowered by 5 ° C. or more is used as an easily sulfonated fiber and dipped in a concentrated sulfuric acid solution to be sulfonated. Proposed. Further, JP-A-8-325932 proposes a sulfonated nonwoven fabric obtained by subjecting a nonwoven fabric composed of sheath-core type composite fibers having a linear low density polyethylene as a sheath component and polypropylene as a core component to a sulfonation treatment. .

[0003]

However, the above battery separator has the following problems. For example, in Japanese Patent Application Laid-Open Nos. 1-132042, 1-132044, and 8-3225932, high-density polyethylene, medium-density polyethylene, low-density polyethylene, and straight chain low-density polyethylene are easily sulfonated. Although various experiments have been attempted, high density polyethylene has excellent adhesive strength, but sulfonation reaction rate is slow, and linear low density polyethylene has excellent sulfonation reaction rate, but adhesive strength is high. It is weak and cannot be said to be sufficiently compatible with respect to the degree of sulfonation and the adhesive strength for use in, for example, a battery separator. In addition, JP-A-7-
According to JP-A-278963, syndiotactic polystyrene fibers generally have poor spinnability, and it is difficult to make them finer, and even if fineness is possible,
Inferior productivity and high cost.

In view of these circumstances, the present invention provides a hydrophilic non-woven fabric which has a cost merit that it can be highly sulfonated even under a mild sulfonation treatment condition and has a small decrease in the strength of the non-woven fabric. And a non-woven fabric for a battery separator that maintains good battery performance while using the same
It was made for the purpose of obtaining a battery .

[0005]

The non-woven fabric for battery separator of the present invention has an ethylene-propylene copolymer having an ethylene content of 3 to 20% by weight or a mixture thereof exposed on at least a part of the fiber surface. comprising a thermoplastic synthetic fiber containing at least 5 wt%, the ethylene - propylene
Polyol having a melting point of 10 ° C or more higher than that of the copolymer
Fineness obtained by dividing the fin-based splittable conjugate fiber into individual components
A fiber assembly containing at least 10% by weight of ultrafine fibers of 0.5 dtex or less, characterized in that the fiber assembly is subjected to a sulfonation treatment.

The thermoplastic synthetic fiber is a sheath-core type composite fiber.
Ethi whose sheath component has an ethylene content of 3 to 20% by weight.
The core is a ren-propylene copolymer or a mixture thereof.
It is preferable that the component is a polyolefin-based polymer because the fiber surface is selectively sulfonated and the decrease in the strength of the nonwoven fabric can be reduced.

The thermoplastic synthetic fiber has an ethylene content of 3 to
Of 20% by weight of ethylene - is the propylene copolymer
In, sulfonation reaction speed is not fast.

The non-woven fabric for a battery separator is preferable in that it is excellent in hydrophilicity and contributes not only to improvement of self-discharge characteristics, but also to excellent liquid injecting property and revolving property when being incorporated in a battery.

A battery incorporating the battery separator is
Excellent battery life and battery capacity are preferred.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The nonwoven fabric for a battery separator of the present invention has an ethylene content of 3 to at least a part of the fiber surface.
20% by weight of ethylene-propylene copolymer or
A fiber assembly containing at least 5% by weight of a thermoplastic synthetic fiber composed of the mixture (hereinafter collectively referred to as EP). The ethylene-propylene copolymer referred to here may be either a random copolymer of ethylene and propylene or a block copolymer, and may be copolymerized with another α-olefin component. Also, with its mixture
Is composed of a mixture with an ethylene-propylene polymer, and may be mixed with other α-olefin component.

If the ethylene content exceeds 20% by weight,
Although it is excellent in heat fusion processability at low temperatures, it slows the sulfonation reaction rate, so it is necessary to lengthen the treatment time or increase the sulfuric acid concentration during the sulfonation treatment, causing damage to other fibers and making it a non-woven fabric. It is not preferable because the strength is significantly reduced.

In the case of ethylene-propylene copolymer, the ethylene content is preferably 3 to 20% by weight. It is more preferably 4 to 10% by weight, and further preferably 5 to 8% by weight. When the ethylene content is less than 3% by weight, the heat fusion processability at low temperature is poor,
If it exceeds 20% by weight, the spinnability is poor. Further, the propylene content is preferably 80 to 97% by weight. It is more preferably 90 to 96 % by weight, and further preferably 92 to 95% by weight. Other α-olefin components may be copolymerized as long as they satisfy the above conditions.
-Butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene and the like.

On the other hand, the ethylene content of the ethylene- propylene copolymer mixture is 3 to 20% by weight.
Is preferred. More preferably, it is 5 to 10% by weight. The ethylene content in the case of being composed of a mixture of ethylene-propylene copolymer means the total amount of ethylene components contained in polyethylene, ethylene-based copolymer, propylene-based polymer or the like. This is because if the ethylene content is less than 3% by weight, the heat fusion processability at low temperature is poor, and if it exceeds 20% by weight, the sulfonation reaction rate becomes slow. The propylene content is 80 to 97.
It is preferably in the weight%. More preferably 90-
It is 95% by weight. Within the range satisfying the above, other α-
The olefin component may be copolymerized, and other α-olefin components include 1-butene, 1-pentene, and 1-butene.
-Hexene, 1-octene, 4-methyl-1-pentene and the like.

The EP is formed in a fiber form exposed on at least a part of the fiber surface. Examples of such a fiber form include a single fiber, a sheath-core type composite fiber, an eccentric sheath-core type composite fiber, a parallel type composite fiber, a split type composite fiber, a sea-island type composite fiber, or a fiber having a circular or irregular cross section. It can be used arbitrarily. Among them, a sheath-core type composite fiber having EP as a sheath component is preferable in that the fiber surface is selectively sulfonated and the decrease in the strength of the nonwoven fabric can be reduced. The thermoplastic polymer used as the core component is not particularly limited, but a polymer having a melting point higher than that of EP by 10 ° C. or more is preferable. For example, polyethylene terephthalate,
Polyester polymer such as polybutylene terephthalate, polyamide polymer such as nylon 6 and nylon 66, homopolymer or copolymer such as polyolefin polymer such as polypropylene and polymethylpentene, and terpolymer. One or two or more can be selected and used. Among them, a polyolefin-based polymer composed of polypropylene or polymethylpentene is preferable in terms of processability, and particularly, the ethylene content is 1% by weight.
A polypropylene of less than 1 is preferable in that the fiber strength after the sulfonation treatment can be highly maintained.

For example, when EP is used for the sheath-core type composite fiber, the composite ratio (volume ratio) of the sheath component and the core component is 10/9.
It is preferably 0 to 90/10. Sheath component is 10%
When it is less than 90%, the adhesion strength is poor and the degree of sulfonation is insufficient, and when it exceeds 90%, the strength of the fiber itself is lowered and the processability is deteriorated.

The fineness of the thermoplastic synthetic fiber made of EP is preferably 0.5 to 5 dtex. If it is less than 0.5 dtex, the processability and quality of the nonwoven fabric are poor, and if it exceeds 5 dtex, the size of voids becomes too large. For example, when it is used as a battery separator, it may cause a short circuit during battery assembly, which is preferable. Absent.

The thermoplastic synthetic fiber made of EP is melt-spun from a single nozzle or a composite nozzle using a known melt spinning machine. The spinning temperature is a temperature at which EP does not deteriorate, and the polymer is extruded at a spinning temperature of 200 to 320 ° C. to produce a spun filament having a predetermined fineness. The spun filament is drawn as necessary. The stretching is carried out at a temperature at which the EP exposed on at least a part of the fiber surface does not fuse, and for example, the stretching temperature is 20 to 90.
Treatment at a temperature of 2 ° C. and a draw ratio of 2 times or more is preferable because the fiber strength is improved. A fiber treatment agent may be attached to the obtained filament. It is preferable to attach a hydrophilic fiber treating agent because the initial hydrophilicity is further improved. Then, if necessary, crimping is applied by a crimping device and cut into a predetermined length to obtain a thermoplastic synthetic fiber made of EP.

The fiber assembly of the present invention contains at least 5% by weight of thermoplastic synthetic fiber made of EP. More preferably, it is 20 to 85% by weight. If the thermoplastic synthetic fiber content is less than 5% by weight, the cost advantage of being highly sulfonated even under mild sulfonation conditions and the production superiority cannot be sufficiently obtained, and the strength of the nonwoven fabric is greatly reduced. Because.

In the fiber assembly of the present invention, the other fiber to be used is not particularly limited, but is composed of a fiber having a melting point higher than the melting point of the thermoplastic synthetic fiber made of EP by 10 ° C. or a decomposition point. , EP is preferable in that the thermal adhesiveness of EP can be effectively utilized. For example, cotton,
Natural fibers such as silk and wool, recycled fibers such as rayon, acrylic fibers, polyester fibers such as polyethylene terephthalate and polybutylene terephthalate, polyamide fibers such as nylon 6 and nylon 66, polyolefins such as polypropylene and polymethylpentene. Fiber or the like is used.

In the present invention, it is particularly preferable that at least 10% by weight of ultrafine fibers having a fineness of 0.5 dtex or less is contained because the liquid absorbing property and the liquid retaining property are improved. The ultrafine fibers having a fineness of 0.5 dtex or less may have any shape, but are preferably two or more types of ultrafine fibers obtained by dividing a splittable conjugate fiber composed of two or more polymer components into each component. .
A splittable conjugate fiber composed of two or more polymer components is
For example, it refers to a fiber having a radial or layered fiber cross section. The combination of thermoplastic polymers used in the splittable conjugate fiber includes a polyolefin-based polymer / polyamide-based polymer, polypropylene / ethylene vinyl alcohol copolymer, polypropylene / polymethylpentene, polypropylene / polyethylene, polymethyl. Examples include pentene / polyethylene, and when three types of polymers are used, the above polymers may be composed of different components. The obtained splittable conjugate fiber is split by a high-pressure water stream treatment or the like described later to form an ultrafine fiber.

For example, in the case of a battery separator, other fibers that can be used include a single fiber made of a polyolefin-based polymer, a sheath-core type composite fiber, an eccentric sheath-core type composite fiber, a parallel type composite fiber, and a split type composite fiber. The use of fibers having a circular or irregular cross section such as fibers and sea-island type composite fibers is preferable from the viewpoint of alkali resistance. In particular, it is preferable to use a polyolefin-based splittable conjugate fiber as the ultrafine fiber having a fineness of 0.5 dtex or less, since the liquid absorbing property and the liquid retaining property are improved and the self-discharge characteristics are improved. At this time, it is preferable that the polymer constituting the polyolefin-based splittable conjugate fiber has a melting point higher by 10 ° C. or more than the melting point of EP, because the thermal adhesiveness of EP can be effectively utilized.

Further, when the hydrophilic non-woven fabric of the present invention is used for a large capacity battery, the fiber assembly is made to have a fineness of 0.5 dtex.
It is effective to use thermoplastic synthetic fibers having a fineness of more than 0.5 and other polyolefin fibers having a fineness of more than 0.5 dtex.

Next, the method for producing the hydrophilic nonwoven fabric of the present invention will be described.

The form of the fiber aggregate containing the thermoplastic synthetic fiber made of the above-mentioned EP is, for example, a dry web obtained by a card method, an air lay method, a wet web obtained by a wet method, or a melt blow method or a spun bond. The fibrous web obtained by a direct method such as a method is used alone, or a fibrous web containing at least one layer and laminating two or more layers is used.
The basis weight of the fiber assembly can be adjusted by the amount of fibers,
Usually, it is desirable that the amount is ²⁰ to 200 g / m ² . Particularly in a battery separator, 30 to 100 g / m ² is preferable.
This is because when the amount is less than 30 g / m ² , the strength of the nonwoven fabric is low, so that a short circuit easily occurs between the positive electrode and the negative electrode, and when it exceeds 100 g / m ² , the air permeability and the like are deteriorated.

Next, the fiber assembly is mechanically entangled by a needle punching method or a spunlace method, a heat-rolling method, a hot-air bonding method, a heat-bonding method such as an ultrasonic bonding method,
Alternatively, they are integrated by combining them. In the present invention, the thermal bonding method in which the thermoplastic synthetic fiber made of EP is melted and used is most effective. For example, when the splittable conjugate fiber is contained, the fiber web is subjected to spunlace treatment to split the splittable conjugate fiber to have a fineness of 0.
It is advisable to form ultrafine fibers of 5 dtex or less and to entangle the fibers.

Then, the above fiber assembly is a fuming sulfuric acid,
A hydrophilic non-woven fabric is obtained by sulfonation treatment using a known sulfonation treatment method such as chlorosulfuric acid, concentrated sulfuric acid or sulfuric anhydride. The degree of sulfonation is preferably at least 0.4% by weight. More preferably, it is at least 0.6% by weight.
This is because if the sulfonation degree is less than 0.4% by weight, the self-discharge of the battery cannot be sufficiently suppressed. In order to promote sulfonation, the nonwoven fabric surface may be activated by ultraviolet rays or radiation and then subjected to sulfonation treatment. Further, the obtained non-woven fabric, dipping method, spray method,
It is preferable to uniformly attach the hydrophilic surfactant by a roll touch method or the like, or to use another hydrophilic treatment method in combination, because the initial hydrophilicity is improved.

The tensile strength in at least one direction of the hydrophilic nonwoven fabric thus obtained is preferably 30 N / 5 cm or more. Particularly, in the battery separator, it is preferably 50 N / 5 cm or more. This is because if the tensile strength is less than 30 N / 5 cm, the rolling property when the battery is assembled is poor.

[0028]

EXAMPLES The contents of the present invention will be described below with reference to examples. The sulfonation rate, tensile strength, liquid retention rate, and capacity retention rate were measured by the following methods.

[Sulfonation degree] (1) Preparation of sample A 5 cm × 5 cm test piece was sampled from the sample, and 13% by weight was obtained.
It was immersed in a KOH aqueous solution for 30 minutes. Then, tap water 3
Wash the sample for 0 minutes, then wash with pure water for 30 minutes.
It was dried at 0 ° C. for 1 hour. (2) Measurement of degree of sulfonation Using a fluorescent X-ray measuring device, the concentration of elemental sulfur in the nonwoven fabric was measured and divided by the concentration of all elements to obtain 100 times the degree of sulfonation. [Tensile Strength] According to JIS L 1096, a sample piece having a width of 5 cm and a length of 15 cm is grasped at a gripping interval of 10 cm, and stretched at a tension rate of 30 cm / min using a constant-speed extension type tensile tester.
The load value at the time of cutting was taken as the tensile strength. [Liquid retention rate] The weight (W) of the test piece in the water equilibrium state is measured up to 1 mg. Then, the test piece was immersed in a KOH solution having a specific gravity of 1.30, the KOH solution was absorbed for 1 hour, then pulled out of the solution and allowed to stand for 10 minutes, and then the weight (W ₁ ) of the test piece was measured and stored. Liquid rate (% by weight) = ((W ₁ −W) / W) × 1
The liquid retention rate was calculated from the formula of 00. [Capacity preservation ratio] A battery separator is sandwiched between a normal nickel electrode and a hydrogen storage alloy negative electrode and impregnated with a KOH solution having a specific gravity of 1.3 as an electrolytic solution, and is SA class Ni-MH.
The battery is charged after initial activation under the same conditions,
The capacity was 2000 mAh. The battery was allowed to stand at 45 ° C. for 2 weeks and the capacity was measured again. The remaining capacity at this time was defined as the capacity preservation ratio. [Preparation of Fiber] (Fiber 1) The sheath component has a melting point of 138 ° C. and an ethylene content of 7
A weight ratio of ethylene-propylene copolymer (manufactured by Japan Polyolefin Co., Ltd.), a polypropylene homopolymer having a melting point of 163 ° C. (manufactured by Japan Polychem Co., Ltd.), a composite ratio of 40/60, and a fineness of 1.7 dtex. , Fiber length 10
mm concentric sheath-core type composite fiber. (Fiber 2) 10% by weight of high-density polyethylene (manufactured by Nippon Polychem Co., Ltd.) having a melting point of 130 ° C. and a melting point of 138
C., 90% by weight of ethylene-propylene copolymer (manufactured by Nippon Polyolefin Co., Ltd.) having an ethylene content of 7% by weight, and a core component of polypropylene homopolymer (manufactured by Japan Polychem Co., Ltd.) having a melting point of 163.degree. , Composite ratio is 5
Concentric-sheath core type composite fiber with 0/50, fineness 1.7 dtex, fiber length 10 mm. (Fiber 3) The sheath component is high-density polyethylene having a melting point of 132 ° C. (manufactured by Nippon Polychem Co., Ltd.), and the core component is a melting point of 163.
℃ polypropylene homopolymer (manufactured by Nippon Polyolefin Co., Ltd.), composite ratio 50/50, fineness 1.7dt
Ex, concentric sheath-core type composite fiber with a fiber length of 10 mm. (Fiber 4) Polymethylpentene having a melting point of 210 ° C. (manufactured by Mitsui Chemicals, Inc.) was used as the first component, and 160 was used as the second component.
As polypropylene (manufactured by Nippon Polychem Co., Ltd.)
A splittable conjugate fiber having a fineness of 2.3 dtex and a fiber length of 6 mm, which has a fiber cross section in which two components are radially split into eight, with a composite ratio of 50/50. (Fiber 5) Fineness 2.2 dtex made of high-density polyethylene (manufactured by Nippon Polychem Co., Ltd.) having a melting point of 130 ° C., fiber length 1
0 mm polyethylene monofilament. (Fiber 6) A polypropylene single fiber having a fineness of 0.9 dtex and a fiber length of 10 mm, which is made of polypropylene having a melting point of 163 ° C. (manufactured by Nippon Polyolefin Co., Ltd.).

[ Reference Examples 1 and 2, Comparative Example 1] Fibers 1 to 3 were prepared, and a slurry was prepared so as to have a concentration of 0.5%, wet papermaking was performed into a sheet, and then a sheath component was prepared. Using a hot plate press adjusted to a temperature 10 ° C. lower than the melting point of 5 MPa, pressurize at 5 MPa for 30 seconds to give a basis weight of 65 g /
A nonwoven fabric of m ² was obtained. The obtained nonwoven fabric was treated with sulfur trioxide gas for 30 seconds and 60 seconds, neutralized with sodium hydroxide, washed with ion-exchanged water, and dried at 60 ° C.

Hydrophilic nonwoven fabrics of Reference Example 1, Reference Example 2 and Comparative Example 1 were obtained. The respective sulfonation degrees are shown in Table 1.

[0032]

[Table 1]

As shown in Table 1, those using the sheath-core type composite fiber made of EP with the sheath component having an ethylene content of less than 20% by weight have a high sulfonation reaction rate and excellent sulfonation treatment efficiency. There is.

Example 1 20% by weight of the fiber 4 and 80% by weight of the fiber 1 were mixed to prepare a slurry having a concentration of 0.5%, wet papermaking was carried out, and the basis weight was 65 g / m ^2. I got the base paper. Then, by injecting a high-pressure columnar water stream from the front and back surfaces of the base paper at a pressure of 8 Mpa, the fibers 4 are divided and the fineness of about 2 dtex is about 0.3 dtex.
Ultrafine fibers of various types were formed, the fibers were entangled with each other, dried at 130 ° C. and heat-bonded at the same time to obtain a nonwoven fabric.
The obtained nonwoven fabric was treated in sulfur trioxide gas for 30 seconds, neutralized with sodium hydroxide, washed with ion-exchanged water, and dried at 60 ° C. A heat calendering treatment was performed to obtain a hydrophilic nonwoven fabric having a basis weight of 65 g / m ² and a thickness of 0.18 mm.

[Example 2 ] 20% by weight of the fiber 4 and 80% by weight of the fiber 2 were mixed to prepare a slurry having a concentration of 0.5%, wet papermaking was performed, and a basis weight of 65 g / m ^{2 was obtained.} I got the base paper. Then, by injecting a high-pressure columnar water stream from the front and back surfaces of the base paper at a pressure of 8 Mpa, the fibers 4 are divided and the fineness of about 2 dtex is about 0.3 dtex.
Ultrafine fibers of various types were formed, the fibers were entangled with each other, dried at 130 ° C. and heat-bonded at the same time to obtain a nonwoven fabric.
Then, a hydrophilic nonwoven fabric having a basis weight of 65 g / m ² and a thickness of 0.18 mm was obtained in the same manner as in Example 1 .

Reference Example 3 20% by weight of fiber 6 and 80% by weight of fiber 1 were mixed to prepare a slurry having a concentration of 0.5%, wet papermaking was performed, and a basis weight of 65 g / m ² The base paper was obtained, dried at 130 ° C. and heat-bonded at the same time to obtain a nonwoven fabric. Then, a hydrophilic nonwoven fabric having a basis weight of 65 g / m ² and a thickness of 0.18 mm was obtained in the same manner as in Example 1 .

[Comparative Example 2] 20% by weight of fiber 4 and 80% by weight of fiber 3 were mixed to prepare a slurry having a concentration of 0.5%, wet papermaking was performed, and a basis weight of 65 g / m ^{2 was obtained.} I got the base paper. Then, by injecting a high-pressure columnar water stream from the front and back surfaces of the base paper at a pressure of 8 Mpa, the fibers 4 are divided and the fineness of about 2 dtex is about 0.3 dtex.
Ultrafine fibers of various types were formed, the fibers were entangled, dried at 135 ° C. and heat-bonded at the same time to obtain a nonwoven fabric.
Then, a hydrophilic nonwoven fabric having a basis weight of 65 g / m ² and a thickness of 0.18 mm was obtained in the same manner as in Example 1 .

Comparative Example 3 A hydrophilic nonwoven fabric having a basis weight of 65 g / m ² and a thickness of 0.18 mm was obtained in the same manner as in Comparative Example 2 except that the fiber 5 was used instead of the fiber 3.

[Comparative Example 4] The nonwoven fabric of Comparative Example 2 was treated in sulfur trioxide gas for 5 minutes, neutralized with sodium hydroxide, washed with ion-exchanged water, and dried at 60 ° C.
Heat-calendered to give a basis weight of 65 g / m ² , thickness of 0.1
An 8 mm hydrophilic non-woven fabric was obtained.

Examples 1 and 2, Reference Example 3 and Comparative Examples 2 to
Table 2 shows the liquid retention rate of No. 4 and the battery performance when used as a battery separator.

[0041]

[Table 2]

In Examples 1 and 2 , the tensile strength was 50.
Since it was highly sulfonated while maintaining N / 5 cm or more, it was excellent in the liquid retention rate and the volume storage rate. On the other hand, in Comparative Examples 2 and 3, the tensile strength was maintained, but the degree of sulfonation was insufficient, and the liquid retention and the battery characteristics were insufficient. In Comparative Example 4, since the sulfonation treatment time was lengthened to promote sulfonation, the capacity retention rate was the same as that of Examples 1 and 2 , but the tensile strength was extremely low and the capacity retention rate was low. It was inferior in handleability such as rolling property.

[0043]

The nonwoven fabric for battery separators of the present invention has an ethylene content of 3 to 20 weight on at least a part of the fiber surface.
Is the amount% ethylene - By propylene copolymer or fiber aggregate its mixed <br/> coalescence contains at least 5% by weight of thermoplastic synthetic fibers are exposed are treated sulfonation, scan sulfonated reaction rate It is suitable because it is fast and has excellent adhesive strength, and there is little decrease in the strength of the nonwoven fabric.

The nonwoven fabric for battery separator of the present invention
A nickel - cadmium battery, a nickel - zinc batteries,
It is suitable for alkaline storage batteries such as nickel-hydrogen batteries, and in particular, the nonwoven fabric for battery separator of the present invention is excellent in hydrophilicity, not only contributes to improvement of self-discharge characteristics, but also liquid injection property when incorporated into batteries. The battery incorporating the battery separator has excellent battery life and battery capacity.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomofumi Tanaka 877, Komiya, Harima-cho, Kako-gun, Hyogo Dai Daiwabo Polytech Co., Ltd. Harima Research Institute (72) Tatsunobu Kida 877, Komiya, Harima-cho, Kako-gun, Hyogo Die Wabo Polytec Co., Ltd. Harima Laboratory (56) Reference JP-A-1-132044 (JP, A) JP-A-9-158020 (JP, A) JP-A-10-172533 (JP, A) JP-A-4 -36954 (JP, A) JP-A-6-207321 (JP, A) JP-A-10-1875 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D04H 1/00- 18/00 H01M 2/14-2/18

Claims (3)

(57) [Claims] 1. At least 5% by weight of a thermoplastic synthetic fiber obtained by exposing an ethylene-propylene copolymer having an ethylene content of 3 to 20% by weight or a mixture thereof on at least a part of the fiber surface, The melting point of the ethylene-propylene copolymer is 10 ° C or lower.
Each of the polyolefin-based splittable composite fibers with high melting point
Small number of ultrafine fibers with a fineness of 0.5 dtex or less divided into various components
A nonwoven fabric for a battery separator, which is a fiber assembly containing at least 10% by weight , wherein the fiber assembly is sulfonated. 2. The thermoplastic synthetic fiber is a sheath-core type composite fiber, the sheath component is an ethylene-propylene copolymer having an ethylene content of 3 to 20% by weight, or a mixture thereof, and the core component is a polyolefin-based polymer. The nonwoven fabric for battery separator according to claim 1, which is a united body. 3. A battery incorporating the nonwoven fabric for battery separator according to claim 1 or 2 .